Weak neutral currents in the U3(W)-gauge theory of weak and electromagnetic interactions

A discussion is given of the implications of the recently proposed U₃(W)-gauge theory of weak and electromagnetic interactions (Pandit 1976) for some phenomena resulting from its weak neutral currents: (1) neutrino-electron scattering, (2) neutrino-nucleon elastic and inelastic scattering, (3) coherent neutrino-nucleus scattering (4) weak interaction effects ine ⁺ e ⁻→μ⁺μ⁻ and (5) parity-violation in atomic physics. The theory agrees quite well with the available experimental results on neutrino processes. We find the coherent neutrino-nucleus cross-section for Fe⁵⁶ to be about 6 times larger than that in the WS-GIM theory giving some hope of accounting for supernova explosion by the resulting neutrino-radiation pressure.     

Nuclear excitation by neutral weak currents

The use of neutrino excitation of nuclear levels to study weak neutral currents is examined.     

Charm production by weak neutral currents

We discuss quantitatively the production of charm in $\text{v}\text{N and}\text{v}\text{N}$ neutral current interactions, and the anomalous lepton events that follow from semi-leptonic charm decay. Diagonal neutral currents, in the Weinberg-Salam model and similar models, predict associated charm production with small cross sections: e.g. $\text{σ(v}\text{N}\text{→ vcc}{}^{\mathrm{?}}\text{X}\text{)/σ(v}\text{N}\text{→ μ}{}^{\mathrm{?}}\text{X}\text{) ? 10}{}^{\mathrm{?2}}$ at high energy. The meagre data on vN → ve⁺X are consistent with a rate of this order. Non-diagonal neutral currents, if present, could give larger cross sections via valence p → c transitions. It should be possible to distinguish diagonal from non-diagonal contributions by their x- or u-dependences, where u = x(1 ? y). We calculate the expected energy distributions of the leptons in characteristic vN → v?⁺X and vN → v?⁺?^?X charm decay events using simple models, and discuss some practical problems in neutral current measurements.     

Effects of neutral weak currents in annihilation

General cross-sections are given for annihilation via one photon and W⁰ exchange. Effects of the W⁰ in the special cases e⁺e^?→μ⁺μ^? and $\text{p}\text{p}\text{→?}{}^{\mathrm{+}}\text{?}{}^{\mathrm{?}}$ at high energies are discussed. These effects are estimated to be comparable to the effects from one γ exchange at energies accesible in NAL and SPS.     

The intermediate weak boson and weak interactions at high energy

The high-energy pire-leptonic weak interaction is investigated based on the assumption of the existence of a charged vector boson which mediates the weak processes. With the aid of the fixed-t dispersion relation the following relation is obtained: The weak boson mass m_W should satisfy $\text{m}{}_{\mathrm{<mtext>W</mtext>}}\text{? G}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}$, with G the Fermi coupling constant, if the asymptotic value of the cross section becomes of the order of the strong interaction in the energy region observable in cosmic rays, etc.The scattering processes $\text{e}\text{+ν→}\text{e}\text{+ν}\text{and}\text{e}\text{+}\text{ν}\text{→}\text{e}\text{+}\text{ν}$ are examined by the aid of the N/D method. For a large vector-boson mass $\text{m}{}_{\mathrm{<mtext>W</mtext>}}\text{?100}\text{GeV}$, an S-wave resonance should exist for the process e+ν→e+ν while for $\text{e}\text{+}\text{ν}\text{→}\text{e}\text{+}\text{ν}$ there should exist a P-wave resonance which corresponds to the intermediate weak boson. The neutral current is then estimated. It is shown that the neutral current produced as a higher-order effect is not inconsistent with the present experiments on the pure-leptonic weak interaction if m_W?1 TeV.     

Hierarchy of symmetry breakings and neutral currents in anSU(6) grand unification model

In anSU(6) grand unification model with eight quarks and eight leptons belonging to 15-plet and singlet representations, the symmetry is spontaneously broken by the sequenceSU(6)SU(3) ^c ×SU(2)×U(1)×U(1)SU(3) ^c ×U(1). Fror two cases of symmetry breakings the effective weak neutral current coupling constants are compared with experiment. For theSU(3) ^c ×SU(2)×U(1)×U(1)×SU(3) ^c ×U(1) symmetry breaking, the coupling constants reproduce the Weinberg-Salam model with a small correction term. Agreement with the experimental mean values is improved with the correction term. Parity violation in atomic physics is also discussed.     

Chiral symmetry and diffractive neutral pion photo- and electroproduction

We show that diffractive production of a single neutral pion in photon-induced reactions at high energy is dynamically suppressed due to the approximate chiral symmetry of QCD. These reactions have been proposed as a test of the odderon-exchange mechanism. We show that the odderon contribution to the amplitude for such reactions vanishes exactly in the chiral limit. This result is obtained in a nonperturbative framework and by using PCAC relations between the amplitudes for neutral pion and axial vector current production.     

Analysis of weak neutral currents using light-cone algebra

Using the algebra of light-cone commutators and making some simplifying assumptions, we have attempted to determine the isospin structure of a two-parameter weak hadronic neutral current. We have also computed in the light-cone model, they distributions for inclusive neutrino and antineutrino neutral current deep-inelastic interactions. Contrary to the quark-parton model, we find that both distributions have the same value.     

Gauge theories and “elastic” weak neutral currents

For the gauge group O(4) × U(1), the alternatives: left-handed leptons are (a) 4-spinors, (b) 4-vectors are shown to imply (a) possible presence, (b) absence of elastic ν_μ ? e and ν_μ ? nucleon amplitude to O(G). Some properties of the new spinor model are described. In contains a neutral current closely akin to the one in the Salam-Ward-Weinberg model.     

SU(4) weak currents

We suggest SU_L(4) ? U(1) as the gauge symmetry of weak and electromagnetic interactions for quartets of quarks and leptons. We analyze how the (additional) SU_L(4) weak currents (besides the SU_L(2) subgroup) could affect the weak interactions of ordinary particles, the atomic parity violation, the neutral-current neutrino reactions and the decays of the τ heavy lepton and the charmed mesons. The suppression of neutral-current parity violation in atomic experiments can be naturally incorporated in this model while at the same time the success of the Weinberg-Salam model with respect to the inclusive neutral current data is kept. The model has limited freedom and therefore many definite predictions.     

Energetic stabilization of d-camphor via weak neutral currents

It is shown via a series of numerical tests on the camphor molecule, C10H16O, that the naturally occurring d-enantiomer is energetically stabilized with respect to its mirror image by electroweak force. The calculated energy difference between enantiomers, about 1.5 x 10(-19) hartree, is roughly eight orders of magnitude smaller than the upper bound suggested by available spectroscopic investigations on the frequency of a spectroscopic transition. However, such a difference is about ten times larger than previous estimates of parity-violating energy contributions reported in the literature for other chiral molecules, which makes the idea of electroweak stabilization of one enantiomer more reliable than expected before.     

UA(1) symmetry restoration at high baryon density

We study the relation between chiral and U_A(1) symmetries in the quark-meson model.Although quarks and mesons are described in mean field approximation,the topological susceptibility characterizing the U_A(1) breaking comprises two components:one controlled by the condensate and the other by the meson fluctuation.The U_A(1)restoration is governed by the competition of these components.In a hot medium,the condensates melt.However,the fluctuation is enhanced.Therefor...     

Spontaneous U（1） symmetry breaking and Bose-Einstein condensation

Based on Bogoliubov's truncated Hamiltonian H_B for a weakly interacting Bose system, and adding a U(1) symmetry breaking term $\sqrt{V}(\lambda a₀+\lambda^*a₀⁺) to H_B, we show by using the coherent state theory and the mean-field approximation rather than the c-number approximations, that the Bose--Einstein condensation(BEC) occurs if and only if the U(1) symmetry of the system is spontaneously broken. The real ground state energy and the justification of the Bogoliubov c-number substitution are given by solving the Schr\"{o}dinger eigenvalue equation and using the self-consistent condition.     

The self-coupling of weak lepton currents in high energy neutrino and muon reactions

The transverse momentum distribution of the muons in the reaction $\text{ν + (z) → ν + μ +}\text{μ}\text{+ (z)}$ is discussed. The lower end of the energy spectrum of the muons in the previous study is also modified by using an improved interpolation formula.     

Space-time structure of weak neutral currents: (II). Elastic scattering

The elastic scattering of neutrinos and antineutrinos on nucleons in which the initial and final nucleon polarizations are measured, is studied from the point of view of the space-time properties of the currents. Structure functions are defined and experimentally measurable quantities which can be usual to disentangle the Lorentz structure of the currents are given. Second class current effects are also examined.